Gauge control apparatus for manufacturing web material



March 3, 1964 E. J. MOORE 3,122,782

GAUGE CONTROL APPARATUS FOR MANUFACTURING WEB MATERIAL Filed June 26, 1961 5 Sheets-Sheet l REFERENCE '5 RADIATION vomcs SOURCE F I 1 1%:22240 RADIATION -|2 COMPARISON RECEIVER cmcun -14 1 RELAY COIL I POWER 1 ROTARY SELECTOR swncn f IZOPIN TERMINAL MOTOR MIG i t CONTROLLER 20 PIN LOCATlON SELECTOR BOARD RELAYS :48 conmzcnon POWER Jr ADJUSTER MOTORS I? VOLTAGE SUPPLY 1 "(RELAY COIL POWER} INVENTOR EDWARD J. MOORE March 3, 1964 MOORE 3,122,782

GAUGE CONTROL APPARATUS FOR MANUFACTURING WEB MATERIAL Filed June 726, 1961 3 SheetsSheet 2 F G. 2 REFERENCE RADIATION H VOLTAGE souRcE V I I l- RADIATION THICKNESS SIGNAL\ CIRCUIT RECEIVER WEB AVERAGE DEVIATIOIIJ VOLTAGE SUPP.Y-RELAY colL POIIIER 3 ROTARY I SELECTOR n swncII I I I I I I CIRCUIT I20 PIN W L- or TERMINAL MOTOR '6 FIGA BOARD CONTROLLER I I I I I zo mmcmon -23 EWING ,43 SELECTOR NOZZLES BOARD I I CORRECTION RELAYS 44 POWER II II '9 PUIIP SPEED ADJUSTER CONTROLLER owns HOPPER 7 E I PP SWITCH I I l I I I I I I I I I L I I I I I I I l I I l I I I I I /I I I I I I I l I 2| INVENTOR 1/ \II \II II I/ \I//\-22 EDWARDIHOURE \\I/ \\l I/ \I/ E a 24 w I I I l I I I I I I 25 I 23 A '9 March 3, 1964 Filed June 26, 1961 E. J- MOORE GAUGE CONTROL APPARATUS FOR MANUFACTURING WEB MATERIAL 3 Sheets-Sheet 3 Fl 6 5 RADIATIGN P [1 SOURCE REFERENCE VOLTAGE I I RADIATION I N 1 RECEWER COMPARISON L k 1 cmcun I VOLTAGE SUPPLY BM POWER n WEB ROTARY SELECTOR l0 swncn J l m Te wn m MOTOR BMRD CONTROLLER J, l t I L0 8A.'5 CORRECTION SELECTOR BOARD POWER RELAYS HOPPER ADJUSTER r r E B. B E Moms M A T INVENTOR EDWARD J. MOORE WWW ATTORNEY United States Patent 3,122,782 GAUGE CGNTRQEL APPARATUS FUR MANUFACTURENG WEB MATERIAL Edward 5. Moore, Tonawanda, N.Y., assignor to E. I. du Pont de Nemours and (Zornpany, Wilmington, Del., a corporation of Delaware Filed June 26, 1961, Ser. No. 119,499 3 (Iiaims. (Ci. 182) This invention relates to an automatic gauge control system useful in the manufacture and processing of web materials. More particularly, it relates to a control system that is useful in manufacturing web materials that have a variable relationship between the extruded dimensions and the finished dimensions.

As is known, the production of plastic film involves the use of a hopper adapted to contain the plastic as a viscous liquid (usually in the molten state) along with extrusion means in the form of orifice-defining lips integral with the hopper. A pump is employed to force the plastic through the lips of the hopper to form the film. The pressure on the material is due to the action of the pump as well as the size of the opening defined by the lips. In the production of extruded film with such apparatus, variations in thickness across the width of the film are not uncommon. These may be due to uneven wear of the lips of the extruder or deficiencies in other mechanical parts of the extruder or to variations in the amount of the extruded material fed to the lips at any particular point across the Width. In the manufacture of plastic films such as cellophane, oriented polyester 1 lms such as Mylar polyester film, and stretched polyolefin films (polyethylene film, polypropylene film, etc.), these thickness variations due to machine problems are further complicated by changes in the width of the material from the point of extrusion to the point of winding up the finished material. Cellophane tends to shrink as it changes its chemical constitution during processing. Stretching of the other films in the longitudinal or transverse direction to improve physical properties tends to change the width of the films. This shrinkage, in the case of cellophane, and width alteration, in the case of the other films, usually does not occur uniformly across the width of the web. Hence, the position of a deviation in the thickness of the material at the windup end does not necessarily correspond directly to that position at the extruder portion of the machine. Experience, however, may teach the operator the location on the extruder at which an adjustment should be applied to correct a specific deviation band observed at the windup end.

Manually controlled systems have been used to adjust these deviations. However, such systems require constant personal attention and are necessarily expensive to operate. Manufacturers in this field have attempted to adopt automatic thickness control systems. volve a direct response between the thickness-sensing element near the Windup end of the machine and the operation of an adjusting element at the extruder. These systems make no allowance for the non-uniform change in width of the material. These systems do not take into account the nature of the specific material being processed that may dictate the place on the extruder that the adjustment must be applied to correct a specific deviation band at the windup end of the machine.

An object of this invention is to provide an automatic gauge control system that can be preset and adjusted if desired to compensate for the width narrowing or widening of a moving web and to compensate for any other variations that may be peculiar to the particular material Registered trademark of E. I. du Pont de Nemours and Company.

These systems inbeing manufactured. Other objects will appear hereinafter.

The objects are accomplished by employing in an automatic gauge control system composed of means for transversely scanning the web, the scanning means adapted to determine the deviation of the web thickness from a reference standard at a particular location on the Web and means responsive to the deviation determination adapted to adjust the thickness of the web, said adjustment means disposed at the web-forming position and at a plurality of locations across the width of the web, the improvement wherein means are interposed between the scanning or thickness-sensing means and the adjustment means, the interposed means adapted to vary the location on the adjustment means at which the adjustment means reacts to the output of the scanning means at any particular location of its transverse scan.

Specifically, the interposed means is composed of two interconnected multiple-juncture terminal boards, the first terminal board communicating with the thickness-sensing device and the second terminal board communicating with the adjustment means, the number of junctures on the first terminal board being substantially greater than the number of junctures on the second terminal board whereby the deviations at several sensing points can be transmitted to a single adjustment point.

The invention will be more clearly understood by referring to the following drawing wherein:

FIGURE 1 is a block diagram illustrating the functional relationship of the basic equipment for carrying out the invention;

FIGURE 2 is a block diagram illustrating a preferred embodiment of the invention;

FIGURE 3 is a View partly schematic of the pinboard circuit distribution element; and

FIGURE 4 is a partial circuit diagram of a means for controlling edge effects in the apparatus of the invention.

FIGURE 5 is a block diagram showing the coaction among the extruder, the extruded sheet, the sensing means and the adjustment means.

Referring to FIGURE '1, a radiation source 11 and receiver 12 are caused to scan back and forth across the moving web 10 by motor 13. Receiver 12 has an output which varies with the thickness of web 10. The radiation source and receiver may be any of several forms known to the art for determination of the thickness of objects by attenuation or absorption of radiation. For example, beta-rays from a radioactive source, X-rays, or optical radiation such as ultraviolet, visible or infrared light, may be employed as the radiation source. The signal from the radiation receiver, which varies according to the thickness of the web, is compared in circuit 14 with an adjustable reference standard voltage from source 15. This comparison produces a signal which varies as the deviation of the thickness of the web from the preselected standard. The magnitude of the deviation is preferably sensed by a slide wire device coupled to a display device, such as a strip-chart recorder (not shown).

An electronic motor speed controller 16 (such as a Thymotrol speed controller, manufactured by the General Electric Company) receives the deviation signal and provides power to control the direction and speed of the adjuster motors according to the sign and magnitude of the thickness deviation. The selection of the appropriate adjuster motor is accomplished through a circuit controlled by the motor 13 which drives the traversing thick ness-sensing elements 11 and 12. The traversing drive motor 13 is mechanically coupled to the movable or rotatable contact of a multiple-pole rotary switch 17. Ro tatabie is used to define the arm which oscillates through a circular are. As the thickness-sensing element 11 and 12 traverses back and forth across the Web, the rotary arm oscillates through a predetermined arc on rotary switch 17. The rotary arm is electrically coupled to a so rce of power to energize the appropriate one of relays 13 which are individually coupled to the adjuster motors 19L Rotation of the rotary contact arm of rotary switch 17 through an arc causes sequential distribution of energy to a plurality of separate channels (126 in the preferred case) according to the instantaneous position of the thickness-sensing element with respect to the width of the web.

The energy is transmitted in a multiple-conductor cable to a multiple-juncture terminal board 23 as shown partly in schematic View in FIGURE 3. Each conductor of the cable terminates in a juncture 21 which has a jack for receiving a removable. jumper wire 22. The jumper wires terminate at junctures of a similar terminal board, 23 of FIGURE 3, having a smaller number of junctures 24. These junctures are further coupled by cable 25 to the adjuster-motor relays 18. By means of the terminal boards and the jumper wires the motor controlling relays can be actuated according to a program preselected on the basis of the shrinkage or the stretching pattern of the Web. The combination of the rotary switch and the terminal boards control the selection and actuation of the relays, and the control signal from the electronic speed controller determines the direction and speed of operation of the adjuster motors.

The rotary switch, pinboard combination is equipped with relay switching devicesso arranged that as the thickness-sensing device transverses toward the edge of the web all of the motor control relays 18 are actuated, but upon the return of the scan, the relays are inactive until the scan reaches about one-third the distance across the web. The operation is repeated at each end of the traverse. tion, since the corrective action would not have been efiective upon immediate reversal of the scan. The use of this arrangement, and the number of motors rendered inoperative is optional, dependent on the relative rate of web travel and the rate of scan, which determines the time lag between sensing and correction.

in the preferred embodiment shown in FIGURE 2, control elements including a resistance circuit, the subject of copending application Serial No. 119,693 filed June 26, 1961, assigned to the assignee of the present application and shown in FIGURE 4, are incorporated to control the signal distribution system. The resistance circuit is coupled to an edge-ensing mechanism to prevent the scanning device 11 and 12 from running over the V edges of the web in the event of sway or irregular shrinkthe motor 13 adjusts potentiometer 32 in the direction required to bring the point 3-9 to the same voltage as point 29. The same motor is also coupled to the rotating selector switch which determines the time of operation of ad uster motors. The potentiometer 33 is mechanically coupled to the thickness-sensing, scanning source and receiver 1i and 12, the combination called the gauge, so that the position of point 29 (and therefore the voltage of point 29) is a function of the gauge position. Point 29 moves from the voltage of 27 to that of 28 as the gauge moves from its home position to the opposite end of the scan, and returns to 27 as the gauge returns to its home position. While this is occurring, the amplifier and motor rotate potentiometer 32, to keep point 39 at the same voltage as 29, except when contact 29 is at a potential above point 37 or below point 36. When the voltage at point 29 reaches the voltage of point '37 or point This is required to prevent doubling the correc 36, the potentiometer 32 will be at one end of its travel. The result is rotation of the selector switch 17 through a predetermined arc as the traversing mechanism scans be 36.

Potentiometers 3-4 and 35 serve as the means for maintaining the traversing mechanism over the web at all times. The voltages at 36 and 37 are determined by the settings along potentiometers 3d and 35, respectively. Potentiometers 34 and 35' are mechanically coupled (in appropriate manner, not shown) to the edging nozzles 43 of a width-sensing device. Hence, the voltages at 35 and 37 are determined by the positions of the web edges. Point 36 is varied through its range (36A tel- 163) as the sheet varies from its outer limit to its inner limit. rotation of the selector switch reaches one end of its arc as point 2? reaches the voltage of point 36. Values in the circuit are selected so that tins occurs as the gauge reaches the edge of the sheet. Similarly, point 37 controls the rotation of the selector oi the rotary switch in the opposite direction. Resistors 38 and 39 are included to improve linearity of the relation between web edge locations and the voltages at 35 and 37, respectively. Limiting resistor 4-9 serves to limit the current, and correspondingly, the voltage between points 35 and 37. Resistors 41 and 42 which are optional make the voltage distribution across 32. non-uniiorm with less voltage change per degree of rotation near the ext emes of the travel of potentiometer contact This requires the motor speed to increase in order to keep the circuit balanced. Power to actuate the relays is transmitted to the rotary contact arm of rotary switch 17, and thence by multiple-conductor cable to the pinboard 29. From this point onward, operation of the control system is identical to that of the embodiment previously described. 7

In the embodiment shown in FIGURE 2, elements to eliminate other deficiencies inherent in the system or created by the system are provided. These include the unit weight control system to reduce long-range drift in the average gauge of the web, and a hopper pressure control to assure uniform extrusion pressure as the lips are opened and closed in response to correction signals.

The unit weight control system comprises an electric drive motor dd geared to the speed control of a positivedisplacement continuously variable pump 45 which supplies the extrusion hopper 46. The control motor on this pump is actuated by the thickness deviation signal selected at several points distributed across the web. These si nals are connected in parallel so that the net signal to the pump control for each traverse of the thickness sensing element represents the average deviation across the web. The control is so coupled that it changes speed of the positive-displacement pump in the direction required to bring the average thickness back to the standard and nullify the deviation signal.

The hopper pressure control device comprises a pressure-operated electric switch 47 which can be set to produce a signal if the pressure goes beyond certain arbitrary limits. A pressure higher than the selected limit produces a signal which is transmitted to the hopper motor relay in the voltage comparison circuit 14 which controls the closing motion of the lips of the hopper and cancels said signal by opening the circuit. A pressure which is lower than the limit would similarly render the lip-opening relay inactive.

Another possibility for the pressure control element incorporates control of the standardization bias, or reference voltage in the voltage comparison circuit 14 instead of cancelling the control signals, as described. In this case, a signal from the hopper pressure-gauge indicating a pressure above the selected limit causes an increase in the bias voltage such that the entire transverse thickness is increased, resulting in a general opening of all lips by an equivalent value, but without cancelling individual control signals.

twee two points determined by the voltages at 3'7 and The Having fully disclosed the invention, what is claimed is:

1. In an apparatus for extruding a web of material composed of a hopper adapted to contain said material for said web; extrusion means composed of orifice-defining lips disposed in integral relationship with said hopper adapted to extrude said material in the form of a web; a pump adapted to force said material through said lips of said extrusion means; wind-up means disposed distant from said extrusion means adapted to collect said web; and adjustment means disposed at said extrusion position of said hopper adapted to adjust the thickness of said web at a plurality of locations across the width of said web; means for transversely scanning the moving web, the scanning means disposed between said extrusion means and said wind-up means adapted to provide an output that is directly related to the deviation of the web thickness from a reference standard at any particular location across the width of the web, said adjustment means being responsive to said output adapted to adjust the thickness of said Web at said plurality of locations across the width of said web; the improvement wherein means are interposed between said scanning means and said adjustment means comprising two interconnected multiple juncture terminal boards, the first terminal board communicating with said scanning means and the second terminal board communicating with said adjustment means, the number of junctures on said first terminal board being substantially greater than the number of junctures on said second terminal board whereby the deviations at several thickness-sensing points can be transmitted to a single adjustment location.

2. An apparatus as in claim 1 wherein the outputs of said scanning means are averaged for each traverse of said scanning means to provide an average output; and said average output is adapted to control the speed of said pump in a manner to bring the average thickness of the web back to the reference standard.

3. An apparatus as in claim 1 wherein control means are interposed between said output and said hopper adapted to control the pressure on said material at said extrusion means between pre-set pressure limits.

References Cited in the file of this patent UNITED STATES PATENTS 2,051,781 Brown Aug. 18, 1936 2,387,718 Coleman Oct. 30, 1945 2,566,854 Rhodes Sept. 4, 1951 2,800,590 Giman July 23, 1957 2,923,971 Nelson Feb. 9, 1960 3,006,225 Mamas Oct. 31, 1961 3,015,129 Hays et a1 Jan. 2, 1962 FOREIGN PATENTS 1,047,276 Germany Dec. 24, 1958 

1. IN AN APPARATUS FOR EXTRUDING A WEB OF MATERIAL COMPOSED OF HOPPER ADAPTED TO CONTAIN SAID MATERIAL FOR SAID WEB; EXTRUSION MEANS COMPOSED OF ORIFICE-DEFINING LIPS DISPOSED IN INTEGRAL RELATIONSHIP WITH SAID HOPPER ADAPTED TO EXTRUDE SAID MATERIAL IN THE FORM OF A WEB; A PUMP ADAPTED TO FORCE SAID MATERIAL THROUGH SAID LIPS OF SAID EXTRUSION MEANS WIND-UP MEANS DISPOSED DISTANT FROM SAID EXTRUSION MEANS ADAPTED TO COLLECT SAID WEB; AND ADJUSTMENT MEANS DISPOSED AT SAID EXTRUSION POSITION OF SAID HOPPER ADAPTED TO ADJUST THE THICKNESS OF SAID WEB AT A PLURALITY OF LOCATIONS ACROSS THE WIDTH OF SAID WEB; MEANS FOR TRANSVERSELY SCANNING THE MOVING WEB, THE SCANNING MEANS DISPOSED BETWEEN SAID EXTRUSION MEANS AND SAID WIND-UP MEANS ADAPTED TO PROVIDE AN OUTPUT THAT IS DIRECTLY RELATED TO THE DEVIATION OF THE WEB THICKNESS FROM A REFERENCE STANDARD AT ANY PARTICULAR LOCATION ACROSS THE WIDTH OF THE WEB, SAID ADJUSTMENT MEANS BEING RESPONSIVE TO SAID OUTPUT ADAPTED TO ADJUST THE THICKNESS OF SAID WEB AT SAID PLURALITY OF LOCATIONS ACROSS THE WIDTH OF SAID WEB; THE IMPROVEMENT WHEREIN MEANS ARE INTERPOSED BETWEEN SAID SCANNING MEANS AND SAID ADJUSTMENT MEANS COMPRISING TWO INTERCONNECTED MULTIPLE JUNCTURE TERMINAL BOARDS, THE FIRST TERMINAL BOARD COMMUNICATING WITH SAID SCANNING MEANS AND THE SECOND TERMINAL BOARD COMMUNICATING WITH SAID ADJUSTMENT MEANS, THE NUMBER OF JUNCTURES ON SAID FIRST TERMINAL BOARD BEING SUBSTANTIALLY GREATER THAN THE NUMBER OF JUNCTURES ON SAID SECOND TERMINAL BOARD WHEREBY THE DEVIATIONS AT SEVERAL THICKNESS-SENSING POINTS CAN BE TRANSMITTED TO A SINGLE ADJUSTMENT LOCATION. 